Much current research has focused on the role of polypeptide growth factors in normal and neoplastic cell growth. It has been hypothesized that some cells become malignant by virtue of the endogenous production of polypeptide growth factors acting on the producer cells through functional external receptors. Such a phenomenon is known as autocrine growth. One growth factor, Interleukin-4 (IL-4), a product of activated T cells, has multiple biological activities that affect cells of most hematopoietic lineages. Among these is the ability to co-stimulate the growth of B cells, T cells and mast cells. Recently, it was found that infection of interleukin-3 dependent mast lines with Abelson murine leukemia virus resulted in loss of growth factor dependence and a transformed phenotype. These cells did not produce autocrine IL-3 but a majority of cells expressed large amounts of IL-4 mRNA and IL-4 biological activity compared to non-transformed mast cells. This project proposes to 1) determine whether IL-4 acts as an autocrine growth factor for transformed mast cells and thus plays a role in the malignant phenotype of these cells and 2) identify cis and trans acting regulatory elements responsible for high constitutive expression of the IL-4 in transformed cells as well as in physiological activation of the gene. Eucaryotic expression vectors containing the IL-4 gene will be introduced into non-transformed mast cells and the consequences of high constitutive expression of factor dependence and tumorigenicity will be examined. Anti-sense oligonucleotides corresponding to regions critical for the initiation of translation of the IL-4 mRNA will be employed during culture of transformed mast cells in an attempt to block protein production. The effect of such treatment on in vitro growth will be examined. In addition, the elements regulating the transcriptional activity of the IL-4 gene in both constitutive high IL-4 expressors and inducible cells will be studied using DNAse I hypersensitivity, DNA methylation, transient expression systems using reporter fusion gene constructs and DNA protein binding assays.